Security Level:
2008-11-3
How to Analyze Crossed Feeder Issue by DT
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HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Outline • What is crossed feeder issue
• The problems raised by crossed feeder issue
• How to detect crossed feeder issue by DT
What is crossed feeder issue (1) The term crossed feeder is used to describe the problem that arises when the feeders for two or more sectors in a site are inadvertently connected incorrectly. For Example, consider a new cell site that has three sectors, A, B, and C:
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What is crossed feeder issue (2)
The crossed feeder problem would arise if the feeder for sector A is connected to sector C and vice versa. When this happens, the sectors typically continue to provide good coverage. However, the network parameters for the two sectors are also reversed. For example, the parameters storing the sectors' BCCH and lists of adjacent sectors would be swapped.
For example, suppose we run a drive test through the area served by the cell whose feeders are crossed display the ServBCCH attribute on the Map while the cell sectors are colored by BCCH. This is what we might see:
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What is crossed feeder issue (3)
There are server types of crossed feeder:
Crossed transmit feeders
Crossed receive feeders
Crossed transmit and receive feeders
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The problems raised by crossed feeder issue
Normal Situation
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Crossed Feeder Situation
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The problems raised by crossed feeder issue
Crossed feeder will raise many problems, such as:
A greater degree of interference
A poor uplink signal strength
A poor performance of handover
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How to detect crossed feeder issue by DT
Crossed transmit feeders Crossed transmit feeders will result in the swap of 2 or more sectors BCCH frequency and TCH’s. As the sectors are pointing in the incorrect direction, performance will suffer as the frequency plan has been changed and a greater degree of interference will be present. In DT, we will find that the handset receives the single which shouldn't have been received in the current cell.
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How to detect crossed feeder issue by DT
Crossed transmit feeders
In the example shown above, point A is in the area of coverage of Cell D3, but the handset at point A receives the stronger signal of Cell D2. It indicates that TX feeders were crossed between Cell D3 and Cell D2.
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How to detect crossed feeder issue by DT
Crossed receive feeders It is not easy to detect this fault by DT, because the BCCH
frequencies will appear exactly as they were designed. However, the statistics for the cell would help us to detect the fault:
Uplink signal strength would be very poor
Link balance would be larger than expected
Handover success rate would be very low
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How to detect crossed feeder issue by DT
Crossed receive feeders The MR measurement is very useful in detecting this type of feeder cross. Uplink-and-Downlink Balance Measurement per TRX and TCH Receive Level Measurement per TRX maybe are the most useful statistics . For example, if the uplink-and-downlink balance is always in level 10 or level 11, we can consider that there is something wrong in the receive path of the site, crossed receive feeder is a possible problem. HUAWEI TECHNOLOGIES CO., LTD.
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How to detect crossed feeder issue by DT
Crossed transmit and receive feeder The symptom is similar with the fault “crossed transmit
feeder”, and we can detect the fault by DT easily .
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